The translation of a surface profile into a quantifiable record is commonly performed with either digital or analog devices that have one component that measures linear position parallel to the surface and another component that measures a relative distance normal to the surface. In the most simplistic method, a straight edged linear measurement device, such as a ruler, is laid on the surface and a second linear measurement device is used to quantify the normal distance from the straight edge to the surface. In most cases, the surface is contacted with the tip of a linear measurement device, positioned perpendicular to the general plane of the surface. In the case of a horizontal surface, the measurement device indicates the vertical position of the tip relative to its horizontal position along the surface. A record of the vertical position of the tip is made either by an attachment to the tip itself, such as a pen onto graph paper, electronically, such as data acquisition software in a computer, or manually by the operator of the device. Resolution of the recorded data is dependent upon the ability of the normal linear measurement device to maintain contact with the surface while maintaining orientation normal to the surface and the ability of the tip to fit into any crevices along the surface.
In measurement devices that use non-contact technology to determine the normal distance from its face to the surface, the relative horizontal placement is generally accomplished with sophisticated components such as rate gyroscopes. These devices are typically robotic in nature and self-propelled along the surface. For this type of device, resolution parallel to the surface relies on the accuracy of the transportation device. The functionality of this type of device is limited to horizontal surfaces. In addition, the complexity of this type of device translates to high cost.